This invention concerns a pneumatic thread holder for a selvedge device on weaving machines.
It is known that cloths with selvedges can be made by successively weaving in the free ends of the weft threads between leno threads, holding these weft threads between the edge of the cloth and the leno threads by means of a thread holder, cutting the weft threads at the same place each time between the thread holder and leno threads, and finally drawing back the free weft thread ends by means of a tucker needle and tucking them into the next shed. Such a known device always uses either mechanical or pneumatic means to hold the weft thread close to the cloth and/or to tuck the weft thread end into the next shed.
In the case of thread holders in which the thread, before it is cut to length, is held by means of an air current, it has been observed that the passage of some object, for instance a tucking needle, in front of the pneumatic holder causes disturbances in the air current which is meant to hold the weft thread, so that the thread does not remain in the correct place necessary to transfer it to the actual insertion device, for example the tucking needle. At the moment that an object passes in front of the pneumatic thread holder so that it comes into the air current, air current reflections and/or deviations and/or eddies are produced, as a result of which the weft thread can wander and even come free of the pneumatic holder, which always results in a fault in the selvedge.